Intruder
by FioLeegion
Summary: Fionna is by herself at the tree house during a knife storm. What happens when she realizes she's actually not alone?
1. Shadow

**This is my first fanfiction…I do not own Adventure Time.**

Fionna stared out the tree house window at the knife storm. Millions of sharp, deadly blades plummeted toward the earth. There is _no way_ she is going out there today. _Sigh._ _This is going to be a long, boring day_, she thought.

_SLAM!_

_What the bazoobs was that?!_ She wondered. She left her room and entered the kitchen to investigate the strange sound. Cold water slowly dripped from the faucet and into the sink. It was eerily quiet. _I swear I heard something_, Fionna thought, disconcerted. A freezing gust of wind caught her off guard, and she looked up to see that the window was open. She reached up and closed it. All of a sudden, there was the sound of something heavy being dropped! Fionna sprinted down to the treasure room, following the noise. It was pitch black, but it looked like…was that treasure chest tipped over before? Suddenly she got the chilling feeling that something was very close behind her, and whirling around just in time she saw a shadow escape up the ladder! She ran back to the kitchen. Looking up, she saw that the window from before had blown open again; the wind had picked up tremendously. As she watched a knife was blown through the window! She lunged out of the way before it could impale her, but heard a screech of pain behind her. However, when she turned around, all she caught a glimpse of was the same shadow as before retreating up to her bedroom.

Fionna set her face into a look of determination. She was scared, but she had to protect her house. And now, whatever this thing was had been wounded. She could sneak up and ambush it! One by one, the brave adventuress climbed the rungs of the wooden ladder. _Deep breaths, in and out. You can do this_. When she reached the top of the ladder, she slowly and quietly peered up over into the room. The candle had been blown out, and she could just make out the outline of her bed and the window, which offered some light. Fionna pulled herself up, careful not to make a sound so as to not startle the creature. When she had gotten into a standing position, a curled-up being was revealed in the corner. She could see little drops of blood on the floor, leading to the shadow. Ever so deliberately, she crept closer and closer to the figure. When she was within striking distance, she pulled a blanket over its head. The monster reacted immediately, flailing about and trying to get free. Eventually Fionna managed to wrestle it to the ground and tie it up in the blanket. She could now see that underneath was the form of a person, so it must be some sort of goblin thief. In one swift motion, she pulled the blanket from where its head should be, revealing—a…a…a _teenager_. He looked like a human, but his skin practically shone in the light from the window. At this point, he had stopped struggling, accepting his fate of being discovered. The courageous girl stood back and took out her sword, prepared to ask some questions. "Who are you and what the flip are you doing in my tree house?!" The boy looked up at her, hurt by wherever the knife had struck him, and answered:

"My name is Marshall Lee. I…I was planning to rob your house and get out, but then the knife storm started, and I was trapped."

Fionna pressed her sword farther toward the young man, and said: "Rob my house, huh?! Who do you think you are? I'm a hero, and it's my job to stop evil like you!"

He looked pleadingly up at her and said, "I…I'm the vampire king, so I guess I'm as stereotypically evil as you can get. But…I know you want to bring me to justice or whatever, but first can you help me not bleed out?"

She looked down and saw that the knife had struck him in the forearm, and the state of the wound was not very good. "…Fine. I'll help you, because even villains don't deserve to die."

He smiled a half-pained, half-grateful grin, revealing a set of dazzlingly white teeth, two of which confirmed that he was indeed a _vampire_. Fionna didn't know much about vampires, but she knew enough to stay away from them—they were pure evil. She dragged the boy by the wrist of his good arm, setting him down on a chair in the kitchen. She dug through a cabinet, pulling out bandages and all that she'd need to fix up his arm. He remained on the stool the entire time, probably because he knew it was a bad idea to try and escape—one bleeding arm, one deadly knife storm. She took about ten minutes to clean and dress his wound, and Marshall tried not to wince in pain. She looked through the cabinet once again and found some pain killer, and after giving this to him, she turned to put everything back in the cabinet. However, when Fionna turned back around, the vampire king was nowhere in sight! _Glob darn it,_ she thought angrily. "The knife storm is still raging outside, so where could he have—AAAAAAAH!"

"Boo." Said Marshall Lee, after she had turned around and found him floating inches away from her. He grinned once again, flashing his teeth. Fionna backed up a few steps, but he just flew closer again. "So I don't really understand…why does a good little hero like you even care if I'm hurt?" He asked. She continued to back up, edging closer and closer toward the wall. "That's just it…I'm a _hero_, it's my duty to help everyone in need, even if they're…scum like you."

"Hmph. I suppose that I _am_ scum. Even so, it's not like I'm some heartless monster. Right?"

"I…I guess so…?" At this point Fionna's back was beginning to press up against the wall. She realized her sword was upstairs in her room—there was no way of reaching the ladder on the other side of the kitchen. As the two became uncomfortably closer and closer, she was forced to look into the vampire's eyes. They were deep red, and she soon found herself entranced in them…What had he said? The vampire laughed when he realized she had missed the question. "I said, you and I aren't so different, are we?" Fionna narrowed her eyes.

"I have never _dreamt _of stealing anything." Marshall's face drifted ever closer to hers, the space between them only centimeters. He knew she was defenseless. "Well, I didn't actually steal anything, did I?"

"I…I guess not. But…you had the _intention_ of stealing treasure."

"Did I? Or did I plan on stealing something else?" As his face was nearly touching hers, he was in perfect striking distance. "Wh…what do you mean?" Marshall suddenly darted forward; Fionna clamped her eyes shut and prepared for the worst, but instead of attacking her, he kissed her on the forehead. With that, Marshall Lee flew swiftly out the window. Fionna opened her eyes and stared at the window in confusion. She touched her fingers up to her forehead, wondering about the vampire boy. _Was he really trying to steal treasure, and tried to confuse me as a distraction so he could escape? What did he mean by 'Or did I plan on stealing something else?' Is that related to…_ Did he like her? Had he come only for her, or did his plans of stealing change when she helped him with his wound? No, Fionna decided—she'd just have to go ask him.


	2. Somewhere Up There

**Fionna's POV**

I exited the tree house, anxious to know the answer to all my questions. _Where would he be, though…Vampires live in dark places, right? I'll check the forest._ So I set off in the direction of Marshall Lee (possibly). I finally reached the edge of the forest, and began wandering down a path.

**Marshall Lee's POV**

I'm sitting on the branch of a tree, very high up in the air. No matter how hard I try, I can't stop thinking about that hero girl. _I don't even know her name. Why is this happening?_ As I'm contemplating this, I see a bunny pass underneath my tree…wait a minute…

**3****rd**** Person Omniscient (I think)**

Fionna passes by a rather large tree, thinking about how huge this forest is. _I'll never find him, he could be anywhere in Aaa!_ All of a sudden, she feels two arms wrap around her waist and then the ground is disappearing beneath her! She screams as she is lifted up into the air. Marshall smirks and pulls her into his arms bridal style, flying ever higher into the sky. The knife storm clouds have moved toward the Ice Kingdom, so they are safe for now, and the sky is still dark enough for Marshall not to burn. "What are you doing?!" she demanded.

"I could ask you the same thing." Fionna blushed, she _was_ the one who had come after him. "Wait a second, I think I get it. You _like_ me, don't you?" At this, Fionna's face flushed bright red. "No I don't! You're a thief and, you're evil, and…" She found herself once again entranced in his beautiful eyes. Marshall laughed. "That _is_ it! You helped me because you thought I was dreamy, and now you're coming after me because you can't get enough of me!"

"That couldn't be farther from the truth! I _helped_ you because you could've died! I came after you because…I…wanted to ask you something…_Right!_ What you said about 'Or did I plan on stealing something else?', if anything that shows that _you're_ the one who likes _me!_"

"What? No! I was just…trying to get you off your guard so I could escape!"

Neither would admit to anything at the moment because of their pride, but they were equally wrong—they _both_ liked each other. After Fionna had helped Marshall, he discovered her kindness. He realized that she was compassionate _and_ beautiful…when you fall for someone, you start to see them as the most amazing creature in the world. Likewise, Fionna had realized that Marshall wasn't pure evil, maybe just misunderstood, and that he was capable of being sweet.

"Admit it. You like me."

"No, you admit you like _me!_"

"Maybe I do like you. So what? You know you like me just as much!"

"Well then we're in agreement!"

Fionna grabbed Marshall's collar and pulled him into a kiss. He moved his hand up to her hair, playing with it. The kiss deepened, and goose bumps spread all over Fionna's body. Marshall felt like electricity was running throughout his entire system. It felt so good, and both of them wanted to keep this feeling forever, but each was out of breath.

When they pulled away each looked at the other with a mixed expression of surprise, happiness, and love. But mostly love. It was a love-at-first-burglary type thing. They didn't understand how their relationship had turned from enemies to more than friends so fast. The two had chemistry, there was no doubt about that.

"So…uh…what now?" Fionna asked. Marshall smirked.

"Well, it's obvious that you're not gonna hand me over to the Banana Guard, because you dig me too much." Fionna punched him in his good arm.

"Haha, just kidding. But no, I…honestly I do really like you. I don't know why, I can't really explain it, but I just feel…like I was meant to be with you." Marshall said. Fionna smiled.

"I feel the same way. Even if you are a delinquent. But don't worry about that, I'll make a do-gooder out of you."

"Pffft. Good luck with that." He laughed, and she couldn't resist laughing too.

"This is great and all, but can you…y'know, put me down now?" Marshall looked down. They were about 100 feet off the ground.

"Oh, uh yeah. Yeah, that's probably a good idea." He slowly lowered the two of them to the ground, careful to avoid the tree branches.

**I think I might continue this…I'm not sure.**


	3. Taken

Marshall continued to float closer to the ground. "Hey, so, this sounds weird, but I don't actually know your name yet."

"My name's Fionna." She answered.

"Fionna. I like that name." She blushed, and he chuckled.

He was a few feet from the ground now. He blinked once and WHERE THE FLIP DID FIONNA GO?! One second she had been in his arms, now he couldn't see her anywhere. He looked up and found his answer.

Fionna was in the talons of a giant bird, who had presumably swooped down and taken her, and was now flying away toward the Candy Kingdom.

_Glob dang it Morrow!_ Gumbutt should really put that thing in a cage or something. Or…what if he had told Morrow to bring him Fionna? No sir, that sugar-coated pansy was not going to steal Fionna from him!

He hissed in exasperation and flew up, soaring over the treetops. He could barely see Morrow in the distance, but he wasn't about to lose sight of that glob-forsaken bird.

"Get back here with my bunny!" he shouted. Morrow apparently didn't hear him at all. As he came closer and closer to the giant bird, he could just make out Fionna's white bunny ears. They soared over hills, trees, and ponds at a great speed.

They were almost to the Candy Kingdom at this point. Marshall put all his energy into his flying, almost overtaking Morrow. When he got close enough he tackled the huge feathery monstrosity to the ground.

They plummeted toward the sugary earth at top speed. Marshall realized this in time and tried to steer them toward the moat. They crashed just inside the walls, landing in the moat and sending up a giant shower of sticky liquid.

Any of the candy people in the vicinity were doused with it, and came over to investigate what had happened.

Marshall had ended up face down in the moat, and when he came to he realized that Fionna was passed out underneath Morrow!

"Fionna!" He ran over to her, using his vampire strength to push Morrow off of her. The bird looked fine; it was Fionna who looked less than okay. "Fionna! Speak to me!"

He realized that maybe she had been underneath the surface of the moat, and her lungs could be full of that nasty sticky stuff. He started to give her CPR, but when he got to the mouth-to-mouth part her eyes opened. He saw this and leaned back to give her space.

"What the lump, dude?" she had no idea what was going on; why was she in the Candy Kingdom now? She remembered being taken away by Morrow, but then…

"Fionna! You're okay!" Marshall leaned in and hugged her tightly.

"Yeah! Why wouldn't I be…oh." She looked around and put the pieces together of what had happened. Confused candy people soaked, Morrow angrily shaking sticky stuff off of its feathers, her blacking out…

"Wait, so why did Morrow kidnap me?" she asked, still confused on that part.

"Because I sent him for you." Marshall narrowed his eyes. He knew that voice. He looked up and no surprise—_Prince Gumball_.


	4. No Worries

"What is wrong with you?!"

They stood in the Candy Kingdom infirmary, where Fionna was getting her arm patched up.

Prince Gumball frowned. "What do you mean, Marshall Lee?"

"What I _mean_ is why do you think it's okay to kidnap little girls at random? Do you see what happened to her?!"

"I believe it was your fault that Morrow crashed." He retorted. Marshall glowered. Technically that _was_ his fault…

"Well, maybe if a giant bird hadn't flown off with Fionna to who knows where, I would've reacted better! A simple 'Oh hey Fionna, can you come over here' would've worked just fine! I wasn't sure if your giant falcon was picking her up for a playdate or taking her to her doom! What if Morrow ate her?!"

"Really, Marshall Lee, Morrow would never do that, he is trained very well." Gumball said, frowning.

Marshall sighed. "I'm really sorry Fionna, I was just worried about you, I'm sorry your arm is all jacked up now…"

But Fionna just smiled. "It's okay; that was actually pretty fun. I've never been that high up before, it was like I was hang-gliding or something! Or like a giant zip line into…whatever that stuff is you guys put in the moat, is that like caramel or something? And anyway, this isn't even my sword arm! It's all good dude."

Marshall breathed a sigh of relief. Fionna was so good-natured and optimistic. The complete opposite of him…While Fionna continued to debate with Doctor Ice Cream what they put in the moat, Marshall turned to Prince Gumball.

"Look, I'm gonna try to be nice to you for once. Why did you need Fionna so urgently?" Marshall asked.

"Oh my! I completely forgot about that! You see, there is a giant toffee monster attacking the candy kingdom!" Gumball replied.

"…I feel like it could also be like, orange soda or something WAIT WHAT? Did you say Toffee monster?" At the mention of a monster Fionna was up and grabbing for her sword.

"Whoa whoa whoa. You can't go fighting some candy monster like this! We'll take care of it," Marshall said, then looking at Prince Gumball decided, "_I'll_ take care of it."

"Aw, c'mon dude, I still got my sword arm!" Fionna protested.

"No way. I got this one." Marshall said, leaning down to kiss Fionna on the forehead. She blushed, but decided not to protest anymore.

Marshall exited the infirmary. Gumball had insisted on coming along with him, and the vampire king decided to humor him.

"So, are you and Fionna dating now or something?" Gumball asked.

Marshall awkwardly scratched his head. "Um, I…guess so? Maybe we would've figured that out if you hadn't abducted her."

Gumball sighed. "I'm sorry, okay? Fionna was the only one who could save the candy people."

"Hey, I could've saved them just fine." Marshall said.

"Well, you and I aren't exactly on…good terms." They rounded a corner and saw a giant, gooey thing smashing candy houses.

"Well, that would be the toffee monster." Marshall said. He looked over at Prince Gumball. "How are you going to attack this thing, you don't exactly have any powers, and—whoa, okay." Prince Gumball had pulled out a giant candy sword, seemingly from nowhere. "Alright then, that works."

Marshall transformed into a giant bat and ran toward the sticky abomination. Gumball ran as well, but not nearly as fast considering how small his legs were compared to Marshall Lee's.

Marshall tackled the beast to the ground, and Gumball started attacking it with his sword. Marshall glanced over at the fountain a few feet away and got an idea. "Hey ugly, over here!" The monster angrily lumbered toward him, picking up speed. Marshall jumped out of the way before the toffee monster crashed into the fountain and dissolved.

"Hah! Took care of that, no problem." Marshall said, proud of himself.

"Yes, thank you for destroying my fountain." Gumball said sarcastically."

"Oh, shut up."

The two walked back to the infirmary.


	5. Really, Fionna?

Marshall and Prince Gumball finally arrived back at the infirmary. Marshall pulled away the curtain to reveal Fionna's bed but…no Fionna. Marshall rolled his eyes; he knew something like this would happen. "Doctor Ice Cream, do you know where Fionna ran off to?"

Doctor Ice Cream turned around, looking rather amused, and told him, "She ran off when somebody came in saying something about a group candy thieves."

"Dear glob, she can't go taking on evildoers all banged up like that! C'mon Gumbutt, let's go get her." Marshall and Gumball went off again, this time in search of the never-tiring adventuress. When they found her, she was fighting four thugs, and two were already on the ground.

"Fionna!" Marshall rushed in and vampire-kicked one of the robbers. Gumball went to work on another with his candy sword. Fionna continued to hack at the remaining two, and soon all six of the thieves were down. The Banana Guard arrived on the scene soon enough, and took all the thieves away.

While Gumball surveyed the scene, a timer went off on his candy watch. He looked at it, then said, "I would love to stay and chat, but I've got some royal duties to attend to," He turned to walk back to his palace. After he had left, Marshall assumed his what-were-you-thinking face.

"Fionna! Taking on six candy thieves with a messed-up arm? Really?"

Fionna frowned. "I'm more than capable of handling monsters by myself, even with my injury." She stared off into the distance toward the Candy Castle. "And I didn't know that Gumball could fight."

Marshall sighed, "Apparently. If you're going to keep changing the subject, I might as well drop it. Does your arm feel any better?"

She looked down at her bandaged arm, thought for a second, and then answered, smiling, "Yeah, I guess. But I think a kiss would make it feel even better."

Marshall smirked, and leaned down to kiss her arm. Then, reconsidering, he met her lips instead. He wrapped his arms around her, careful to avoid her bad arm—_funny, now we both have a bad arm_—and she put her good arm around his neck. It only lasted a few seconds, but it filled Fionna with warmth—it actually _did_ make her arm seem to hurt less.

When Marshall pulled away, he put one arm around her waist and they started to walk through the Candy market. "We have a really strange relationship, huh?" Fionna mused.

"Yeah…but I'm really glad I met you." Marshall said, grinning.

"So…when you broke into my house, what were you…I mean, before you left you said…" Fionna broke off.

Marshall smiled. "To be honest, at first I really _was_ there for the treasure. I came in through the kitchen window cuz it was unlocked, and I found that chest in the treasure room. I picked it up and started going outside, but then the knife storm clouds rushed in, almost out of nowhere. And to think, getting in and out of there had seemed too easy…I ran back in, slammed the door, and, well, I accidentally dropped the chest. I figured anyone in the house would have heard me by then, so I hid, and you know the rest from there. But, when you…you helped me, I started to feel really bad for breaking into your house, and you seemed so nice, and pretty, and heroic, and…" He trailed off. Fionna only smiled.

She leaned up to kiss him on the cheek. "Thanks."


End file.
